The present invention relates to a device for measuring muscular strength and more particularly to the measurement of the strength of the intrinsic hand muscles innervated by the median nerve after it passes through the carpal tunnel in order to provide an objective indication of the presence of carpal tunnel syndrome.
Generally, the median nerve supplies sensation to the thumb, index finger, middle finger and half of the ring finger. The nerve passes through the wrist beneath the flexor retinaculum or transverse carpal ligament. The transverse carpal ligament and tendons of the flexor muscles define a tunnel through which the median nerve passes. The median nerve innervates three thenar and two lumbrical muscles. Other short muscles of the hand are innervated by the ulnar nerve. The muscles innervated by the median nerve include the abductor pollicis brevis, the opponens pollicis and the superficial head of the flexor pollicis brevis.
Should the median nerve become swollen as it passes through the carpal tunnel or should the carpal ligament become abnormally thickened, pinching or compression of the median nerve results. Swelling of the nerve or surrounding tissues may result from certain diseases, such as diabetes mellitus or rheumatoid arthritis. Unusual strain on the wrist such as that caused by repetitive and strenuous use of the hand may also result in such swelling. When such occurs, the resulting symptoms are referred to as carpal tunnel syndrome. The symptoms include pain, loss of sensation and weakness in the hand.
Generally, diagnosis of carpal tunnel syndrome will not occur until long after onset of the symptoms. Presently, there is no objective way to measure weakness in the hand which might be related to carpal tunnel syndrome and which would provide an early identification of the problem. The earlier diagnosis is accomplished, the more effective treatment procedures will be. If detected early, carpal tunnel syndrome may be treated and relief obtained short of surgical procedures. Surgical procedures are not always effective. Carpal tunnel syndrome is a significant factor in the work place resulting in lost work time and compensation claims. Early identification and treatment may reduce the cost associated with th disease.
A need exists for a device and method which can detect weakness in the hand which may be related to carpal tunnel syndrome and which will provide objective parameters which indicate the need for further evaluation.